RESPIRATION. 95 



tissue placed within the fold. These are called the true vocal 

 cords, being alone employed in the production of the voice. 

 The upper folds are called the false vocal cords. 



5. The Voice. There is a V-shaped space or chink 

 between the true vocal cords, through which the air passes 

 to and from the lungs. This chink may be narrowed or 

 widened by the action of muscles, while at the same time 

 the cords are made tight or loose like the cords of a musical 

 instrument. It is this power to vary the size of the chink 

 and the tension of the cords which produces the many differ- 

 ent sounds the human voice is capable 

 of uttering. In quiet breathing the 

 air makes no sound, but the moment 

 we tune up the instrument by tighten- 

 ing the cords and lessening the chink, 

 the air makes a noise. The size and 

 length of the vocal cords are not the 

 same in every person, and hence the 

 variety in the pitch of the voice. A 

 short cord on any instrument gives 

 a high pitch, and a long cord gives 



j Tx xl. FIG. 32. -The Larynx as seen 



forth a deep Or low note. It IS the from above : a, 6, c, cartilages 



same in the human voice. In women of the larynx; d, epiglottis 

 and children, the larynx being smaller, 



the cords are shorter than in men, consequently their voices 

 have a higher pitch. 



A musical sound is a prolonged vibration of the vocal 

 cords. The number and variety of sounds produced in sing- 

 ing depend upon the length of the cords and their different 

 degrees of tension. 



Singing is an exceedingly useful exercise in school ; it 

 pleases the sense ; it elevates the mind ; it exercises the 

 muscles of the chest; it trains and develops the vocal cords 

 and increases the capacity of the larynx so that the child 



